BIOMATERIAL ASSIGNMENT
BIOMATERIAL ASSIGNMENT
Biomaterials in Hip Joint
NAME-SURESH KUMAR SWAMI Submitted to-
ID-2015UME1322 Dr. Amit Kumar Singh
Branch-mechanical Assistant Professor
Introduction:-
Total hip joint replacement is unavoidable in the
orthopedic application, for improving the quality of patient life
suffering from arthritis. Replacing damaged joint with artificial joint
gaining popularity and it became a need in such cases. While joint
replacement represents success stories in the field of orthopedic
surgery, but maintaining implant for last long is still challenge. The
average lifespan of hip joint replacement is about 15 years.
Any disease involving hip/knee joint leads to immense difficulty in walking,
and results in severe disability.
The hip joint is a spherical joint between the femoral head and the
acetabulum in the pelvis .
Hip joint is ball and socket joint consisting of:
1. Femoral stem,
2. Femoral head and
3. Acetabular component.
HISTORY:-
The first attempt of hip joint replacement was reported in early 1890 by
using ivory and stainless steel.
In 1962, Sir Charnley developed a cemented stem with a 22.22mm head in
stainless steel combined with a cup made of Ultra High Molecular Weight
Polyethylene (UHMWPE) .
The first metal-on-metal (CoCr-CoCr) total hip replacement (THR) was
unsatisfactory in terms of high friction forces and high rate of wear.
LIMITATION:-
The main limitation in THR is service life of about 15 years, which is not
satisfactory for patients under 60 years of age, about 44% demanding a life
expectancy of 20to 25 years .
Implant failures can be due to a number of factors, but one of the critical
issues is the release of wear particles from bearing surface of the implant.
Accumulation of wear particles leads to bone loss and eventually aseptic
implant loosening. Therefore it is highly desirable to reduce the generation
of wear particles from the implant surface. Infection, wear and breakaway
failure are common reasons for revision of THR surgery
Components of total hip replacement:-
BIOMATERIAL:-
Biomaterials are synthetic materials used to develop parts and replace a
body part or function of the body part in safe and reliable manner.
Biomaterials are used in human body and hence need to be inert and
mechanically strong enough to bear the load.
Biomaterials are expected to work satisfactorily in body environment, where the
pH value of body fluid varies from 1 to 9.
During daily activities bones are subjected to the stress of about 4MPa and mean
load on hip joint is three times the body weight. The peak load on hip joint during
jumping time may be up to 10 times body weight;
again these stresses are repetitive and fluctuating depending upon activity to be
performed .
These conditions indicate the situation where biomaterials to sustain and again
these conditions vary from patient to patient.
Total Hip Joint Replacement Materials:-
a materials problem is one of selecting the right material from the many thousands that
are available. There are several criteria on which the final decision is normally based.
1. the properties required of the material.
2. A second selection consideration is any deterioration of material properties that may
occur during service operation.
3. Now the material used in body should be compatible with body .
Mechanical properties of human bone:-
Material Yield Elongation Vickers Young’s Fatigue
Tensile strength at fracture hardness modulus limit
strength MN/m2 (Hv) GN/m2 GN/m2
MN/m2
137.3 ------- 1.49 26.3 30 ---------
Material available:-
1. Metallic Materials
2. Polymer Materials
3. Composite polymer
4. Highly cross-linked UHMWPE
5. Ceramic Material
6. Alumina-zirconia composites
7. Non oxide ceramic- silicon nitride
Metallic Materials:-
Different metallic material and their mechanical
properties are given below-
Material Material Yield Elongatio Vickers Young’s Fatigue
Tensile strength n at hardness modulus limit
strength MN/m2 fracture (Hv) GN/m2 GN/m2
MN/m2
Ti-6Al-4V 1000 970 12 ------ 121 ----
316l 650 280 45 190 211 0.28
SS(annea
led)
Co-Cr 1540 1050 9 450 541 .49
alloy
Cast Co- 690 290 8 300 241 .30
Cr alloy
Titanium 710 270 30 ---- 121 .30
Stainless steel materials are more resistant to a broad range of corrosive environment due to
high Cr content (more than 12 wt %)of steel.
it allows the formation of a firmly adherent, self-healing and corrosion resistant coating
oxide of Cr2O3.
Despite these properties stainless steel implants are degraded because of pitting, crevice,
corrosion fatigue, fretting corrosion, stress corrosion cracking, and galvanic corrosion in the
body.
Titanium based alloys are also popular in THR, because of its characteristics like low density
(approx. 4700 Kg/m3), high specific strength, good resistance to corrosion due to the
formation of an adhesive TiO2 oxide layer and complete inertness along with
biocompatibility.
Moderate elastic modulus of approximately 110 Gpa, which is only half of that of surgical
stainless steel or cobalt-based alloys and five times that of cortical bone, leads to more
physiologically sound stress distribution in the implant bone. The intermediate layer of
cement does not require in Ti implant.
polymeric Materials:-
Sir John Charnley, introduced metal-on-polyethylene hip prostheses along self-polymerizing
polymethyl-methacrylate (PMMA) bone cement for fixation .
Polymer materials are popular for various applications due to their-
low cost, a wide range of mechanical and physical properties.
Polymers are divided into two categories according to their durability in biological
environments: 1. Biostable and 2.Biodegradable.
Examples of bio stable polymers are polyethylene (PE), poly (methylmethacrylate) (PMMA)
and polyetheretherketone (PEEK) which are used in hip and dental implants. Ultrahigh
molecular weight polyethylene (UHMWPE) has also been used extensively for hip and knee
joints.
Composite polymer:-
While working implant and bone are unevenly loaded, which is called as ‘stress
shielding’ or ‘stress protection’.
In such cases low modulus material like polymer are suitable , but low modulus
associated with little strength restricts the potential use of polymers.
While Performance of UHMWPE is satisfactory for the short term, but for long
term application researcher suggested reinforcing of UHMWPE with carbon
fibers to improve its creep resistance, stiffness and strength.
Reinforcing PEEK with carbon fiber offers superior wear resistance as compared
to unfilled UHMWPE when rubbed against either metal or ceramic .
Highly cross-linked UHMWPE –
In total hip replacement system typically applies ultra-high-molecular-
weight polyethylene (UHMWPE) insert that articulates against a cobalt-
chromium alloy or ceramic to restore the function of a damaged joint.
Although properties of the composite polymer are suitable for THR there is
no appreciable difference in wear rate of reinforced and unreinforced
UHMWPE , the effect of carbon fiber reinforcing on wear characteristic of
UHMWPE is unclear.
Ceramic Material :-
the first alumina (Al2O3) material dedicated for hip joint was patented .
Ceramic are a crystalline structure where atoms are held together by the ionic and
covalent bond.
This ionic bonding gives these compound high compressive strength, hardness and
chemical inertness.
Alumina and zirconia (ZrO2) are oxidized ceramics; their high oxidation level renders them
chemically inert, resistant to corrosion and stable over the long term.
Alumina is commonly used ceramic for THR owning to its low friction and wear coefficient,
makes its suitable alternative for the orthopedic bearing.
Comparative to alumina, zirconia offers 2 to 3 times more flexure strength and fracture
toughness and thus it is most fracture resistant ceramic.
Alumina-zirconia composites -
Mixed composite of ZrO2 and Al2O3 are also used in hip replacement.
these materials are known as ‘zirconia- toughened alumina (ZTA).
It has a hardness of alumina, with improved strength and toughness.
But ZTA is still unstable, as it derives its strength and toughness from the mechanism that
resulted in catastrophic failure of the ZrO2 – based orthopedic material .
Conclusion :-
The basic aim of developing alternative THR materials is to create a joint with low
friction and wear rate with increased strength.
There is continues development of material from early days of metals to
nowadays non oxide ceramic.
Every material has its advantages and disadvantages that must be considered
during application.
Metal on metal and alumina on alumina-based joints are best in tribological
view.
While HXPLE has shown excellent wear resistant with better shock absorption.
Development of ceramic material to nowadays silicon nitride has presented a
very good alternative for hip joint replacement.
The ideal THR material is still needed to be evaluated with the modifying metal
surface, improving the polyethylene and developing composite ceramic.
Coating or addition of boron nitride in non oxide ceramic like silicon nitride
implant material also presents the opportunity of development of future material.
